Read the following passage and mark the letter A, B, C, or D on your answer sheet to Indicate the correct answer to each of the questions from 31 to 35. The term "virus" is derived...

* Hướng dẫn giải

Đáp án A

Thông tin trong bài: 'The nature of viruses made them impossible to detect for many years even after bacteria had been discovered and studied. Not only are viruses too small to be seen with a light microscope, they also cannot be detected through their biological activity, except as it occurs in conjunction with other organisms."